The present invention concerns a process for fixing holding clips to a band which is movable in its longitudinal direction, wherein the band is deformed transversely relative to the longitudinal direction in such a way that the spacing of the band edges becomes less than the band width and the internal spacing of the holding elements provided on the holding clip and the part of the band which is between the band edges is curved forwardly out of the plane of the band defined by the band edges, the band edges are brought into position between the holding elements and the deformation is substantially removed again so that the band edges substantially resume their original spacing and the holding clip comes into frictional engagement with the band.
The present invention also concerns a corresponding apparatus for fixing holding clips to a band or band-like material which is movable in its longitudinal direction, comprising deformation elements for the band, which deform the band in such a way that the spacing of the band edges becomes less than the band width and the internal spacing between holding elements of the holding clips, and guide elements for the band. A process and an apparatus of that kind are known from German laid-open application (DE-OS) No 37 09 412.
Likewise such a process and a corresponding apparatus are also already known from German patent No 2 512 826.
German laid-open application (DE-OS) No 37 09 413 is also concerned with a process and an apparatus for clipping holding clips to a band.
Such processes and apparatuses are used in particular for transporting films or photo paper through a processing machine. For that purpose a film, photo paper or the like which is to be transported through a processing machine is fixed to the end, which is of no further interest here, of the holding clip, while the other end of the holding clip has holding elements for fixing to what is known as a tow band which is driven and which thus transports the holding clip with the film or photo paper fixed thereto through the machine.
The corresponding tow bands generally comprise plastics material or fabric which is insensitive to the processing chemicals, and are more or less elastic. The holding elements of the holding clips, which elements engage the band, generally comprise U-shaped portions which face towards each other with their open sides and the limbs of the U-shapes of which are connected together on one side while on the other side they are open to receive the band between the U-shaped holding elements. In that arrangement the internal spacing of the two free limbs of the U-shapes is smaller than the width of the band and is therefore less than the spacing between the edges of the band. Before corresponding automatic clip fitting apparatuses where introduced, the edges of the band were gripped by hand by an operator and pressed together using the fingers, passed through between the free limbs of the U-shapes of the holding elements and released so that they could slide at both sides into the two U-shaped openings. In that arrangement the total width of the band substantially corresponds to the spacing between the base sides of the two U-shaped holding elements. The width of the U-shaped clip openings approximately corresponds to the thickness of the band so that it is in relatively firm frictional engagement with the clip and entrains same, especially when the clip is loaded at its free end to which the film material or photo paper is fixed.
In addition, another clip is known as disclosed in German laid-open application (DE-OS) No 35 35 852, which for fixing purposes has a substantially square opening with oppositely disposed projections projecting into the opening. Here too the internal spacing of the projections is less than the width of the band while the size of the square opening is moreover substantially the width dimension of the band. For the purposes of fixing such a clip to the band, the two edges of the band are also pressed together and moved from one side to the opening of the clip in such a way that the edges of the band snap into position behind the projections so that in the region of the projections the band is bent around same and is thus also in fixed frictional engagement with the clip.
It will be appreciated that, by means of corresponding processes and apparatuses, it is not only photo paper and films but for example also other material such as webs of paper or plastics material that can be transported in any manner by means of tow bands and for example threaded in printing machines between printing rollers or into other apparatuses for processing or treating the web of material.
For further details of the connection between the clip and the band, attention is directed to the specified state of the art.
The specified apparatuses, with the apparatus options available, substantially precisely emulate the operation which previously was also performed by hand. In the case of German patent specification No 2 512 826 the clip is accommodated in a feed device which is movable perpendicularly to the plane of the band and moved towards the band as soon as the edges of the band are suitably bent together. As soon as the clip has reached the band and the edges of the band have passed the free ends of the limbs of the U-shapes of the holding elements or the projections of the holding elements, the deformation elements release the band and thus allow the edges of the band to snap into position in the holding elements of the band clip.
In the case of the process and the apparatus of German laid-open application (DE-OS) No 37 09 412 the clip is guided prior to and during the clip-application procedure, like the band, parallel to the plane of the band in such a way that the outsides of the free limbs of the U-shapes shapes of the holding elements remain in contact with the edges of the band. By virtue of the above-indicated deformation of the band, the edges of the band are then stressed and pulled away due to the further deformation of the band under the limbs of the U-shapes of the holding elements and snap into the free space between the U-shaped openings, by virtue of the biasing effect. After the deformation ram member is moved back, the edges of the band then slide into the U-shaped openings of the holding elements. However that apparatus which the present invention takes as its basic starting point suffers from some serious disadvantages. The close guidance of the holding clip on the edges of the band, in order to allow it to snap into position between the holding elements, requires the guide elements to be of a very precise shaped configuration. Otherwise, that arrangement may give rise to earlier engagement at one side between an edge of the band and the holding clip so that the latter is tilted and becomes jammed in the narrow guide passage. Even if the guide passages for the band and the holding clip are of a highly precise configuration, that situation can occur by virtue of the fact that the edges of the band suffer from wear which is irregular from one position to another.
Depending on the respective spacing of the holding elements the band must be deformed to a very substantial degree and the ram member or punch must press the central portion of the band very deeply into a suitable die so that the edges of the band spring into position between the holding elements.
In practice, those problems have resulted in a corresponding apparatus being known and produced only in such a configuration that the entire apparatus is also moved along with the generally moving band, during the clip-fitting operation. An alternative to that lies in momentarily stopping the band, which however, in a continuously operating machine, requires a suitable band storage device upstream and downstream of the apparatus, which is highly expensive and complicated. In addition moving the apparatus with the moving band also requires a really expensive and complicated structure.